The present invention relates to an intake plenum unit for a heat exchanger with a tube block made of a plurality of heat exchanger tubes, with the intake plenum unit having a intake plenum with a tube wall which has a common lengthwise slot provided for ends of the heat exchanger tubes to be inserted therein.
An intake plenum unit of this kind is known from EP 0 845 647 A1. In that intake plenum, a lengthwise slot is provided, axially delimited on both sides, into which slot the ends of straight flat tubes of a tube/fin block, twisted by 90 degrees, are inserted in succession in a fluid-tight manner. Because of manufacturing tolerances, especially relating to the width of the flat tubes and hence the length of the twisted tube ends to be inserted therein, this length being parallel to the lengthwise slot of the intake plenum, problems can occur when the tube ends are inserted into the lengthwise slot. For example, if the width of most of the flat tubes in the tube/fin block is at the upper tolerance limit or even exceeds this limit, the length of the lengthwise slot for this purpose can barely suffice, so that all of the tube ends can be inserted only with difficulty into the slot. Conversely, the lengthwise slot can turn out to be too long instead, if the width of the flat tube is at the lower tolerance limit or is below the latter, creating the danger of leaks in the lengthwise slot after the inserted tube ends have been soldered tight.
The technical problem solved by this invention is to provide an intake plenum unit of the type recited at the outset in which the ends of the heat exchanger tubes of a tube block, regardless of manufacturing tolerances, can be inserted reliably fluid-tight in a common lengthwise slot of the intake plenum.
The invention solves this problem by providing an intake plenum unit in which the intake plenum is manufactured from one or more tubes inserted into one another endwise or fitted together, with a lengthwise slot that is open at least at one individual tube end before or after the assembly of the intake plenum, in other words terminating axially. The actual usable length of the intake plenum lengthwise slot formed in this manner from one or more single-tube lengthwise slots for inserting the ends of the heat exchanger tubes is not established in advance but is variable over a wide range which is sufficiently wide to compensate for any manufacturing tolerances that appear along the axial length of the inserted tube ends. After all the tube ends have been inserted into the lengthwise slot, it is then possible to proceed in suitable fashion with the remaining part of the lengthwise slot not occupied by inserted tube ends.
For example, this free lengthwise slot portion can be sealed subsequently or at the same time as the brazing-tight of the inserted tube ends, or the intake plenum can be inserted with this free part of the lengthwise slot fitted tightly into a connecting tube. Alternatively, an intake plenum manufactured from several individual tubes, at least at one end, can include an individual tube, closed at the outer end, with the lengthwise slot open only toward the inner end. The slot is able to be fitted together with an adjacent individual tube with its inner end for a variable distance, so that the length of the lengthwise slot is adjustably variable as a result. According to the invention, therefore, the ends of the heat exchanger tubes can be inserted without difficulty into the common lengthwise slot even when the tube ends exhibit significant inaccuracies in manufacture.
According to one feature of the invention, the intake plenum includes a plurality of extruded individual tubes that are closed and have bottoms at the ends. The tubes are fitted together so they abut one another at their ends, with the intake plenum lengthwise slot preferably being added after the individual tubes have been joined together. The tube bottoms connected to one another then form transverse partitions in the intake plenum.
According to another feature of the invention, a lengthwise slot, open axially on both sides, is provided on each individual tube which, in this case, is made by bending a sheet metal part that was preferably previously flat. If necessary, the sheet metal part can be bent into a tube at the same time as the heat exchanger tube ends are inserted, so that the intake plenum, even in the transverse dimension of its lengthwise slot, can be adapted without difficulty to any manufacturing tolerances in the heat exchanger tube ends in this extension direction. In another construction the two marginal surfaces of the sheet metal part that delimit the lengthwise slot are shaped so that they lie parallel to and opposite one another following the bending of the sheet metal part to form the tube, so that they can fit flush against the flat outer surfaces of the inserted heat exchanger tube ends that are parallel to one another, promoting the stability and tightness of the fitted connection.
Another feature of the invention is that the lengthwise slot can be designed as a feedthrough so that the edges of the lengthwise slot have a form that is directed inward or is bent over outward and, in this fashion, can receive the heat exchanger tube ends flexibly and with a spring action when inserted.
Still another feature of the invention is that the intake plenum unit can include a sleeve that can be pushed onto the respective end area of the intake plenum, surrounding the latter, with the end area being slit from the openly terminating lengthwise slot. The sleeve serves to seal off an endwise portion of the lengthwise slot that may remain free after the heat exchanger tube ends are inserted. For this purpose, the sleeve stabilizes the intake plenum during operation against bending under high operating pressures of a heat exchanger medium flowing in the interior. In another construction the sleeve has a lengthwise slot that is open only at its end that is at the front in the pushing-on direction, the slot serving as an insertion slot for one or more heat exchanger tube ends that are inserted into the intake plenum lengthwise slot in the end area in question. In this case, the sleeve can be pushed on in the vicinity of the part of the intake plenum lengthwise slot that is occupied by inserted tube ends. Pushing may occur, for example, until the end stop of the insertion slot contacts a heat exchanger tube end, so that a portion of the intake plenum lengthwise slot that terminates openly and may be left free can always be reliably covered by the sleeve.
Yet another feature of the invention is that the sleeve may have a closed bottom or be designed to be open at that point and can be closed by a lid applied separately. In any event, as a result, the intake plenum can be closed in a fluid-tight manner at the end in question.
A further feature of the invention is that a mounting mandrel and/or a retaining element, for example a retaining flange, can be formed on the sleeve. In this way, following the mounting of the sleeve on the intake plenum, the intake plenum unit, and with it the associated tube block, can be permanently connected by the mounting mandrel or the retaining element with another part in a desired fashion.
Finally, the intake plenum can be made of a plurality of individual tubes, with at least one of the two endwise tubes being closed at its outer end and provided with a lengthwise slot that is open at its inner end. This endwise tube can be fitted together in variable length with the adjacent individual tube. In this way, a lengthwise slot, closed on both sides and with a variably adjustable length, can be provided, with the heat transfer tubes being added before the complete fitting together and locking of the two abovementioned individual tubes.
Advantageous embodiments of the invention are shown in the drawings and described below.